Position indicator

ABSTRACT

A position indicator system for remote indication of a position of a governing member. The indicator system has two bourdon tubes, the first of which is mechanically connected to the governing member and the second serves as an indicator actuator. The two bourdon tubes are interconnected with a capillary tubing in a closed hydraulic system and transmits the pressure variations generated by the mechanical subjection of the first bourdon tube by the governing member to the bourdon tube in the indicator. A compensating system has an additional pair of bourdon tubes, the first of which is installed at the location of the governing member, and the second of which is installed at the location of the indicator. The bourdon tubes are interconnected with a capillary tubing in a closed hydraulic system. A mechanical connection is provided between the pivotable fitting supporting the second bourdon tube and a free end of the bourdon tube at the indicator position.

United States Patent [1 1 3,641,966 Auerdahl 1 Feb. 15, 1972 [54]POSITION INDICATOR 3,095,745 7/1963 Kirwan ..73/412 [72] Inventor: OlavAuerdahl, Sandvika, Norway Primary Emminer Louis l capozi [73] Assignee:Norsk Hydro A.S., Bygdo Alle, Oslo, Nory Lind & Pollack way [57]ABSTRACT [22] Filed: May 21, 1970 Appl. No.: 39,391

A position indicator system for remote indication of a position of agoverning member. The indicator system has two bourdon tubes, the firstof which is mechanically connected to the governing member and thesecond serves as an indicator actuator. The two bourdon tubes areinterconnected with a capillary tubing in a closed hydraulic system andtransmits the pressure variations generated by the mechanical subjectionof the first bourdon tube by the governing member to the bourdon tube inthe indicator. A compensating system has an additional pair of bourdontubes, the first of which is installed at the location of the governingmember, and the second of which is installed at the location of theindicator. The bourdon tubes are interconnected with a capillary tubingin a closed hydraulic system. A mechanical connection is providedbetween the pivotable fitting supporting the second bourdon tube and afree end of the bourdon tube at the indicator position.

4 Claims, 1 Drawing Figure PATENIEBFEB 15 I972 316411966.

o C E 27 3a I i f 23 o 25 Olav Auerdahl,

INVENTOR ATTORNEY POSITION INDICATOR The present invention relatesgenerally to a position indicator, more particularly to an indicator forremote indication of the position of mechanical elements, for instanceremote indication of the angular position of a butterfly valve.

There is known several kinds of mechanism which are able to meet thisobject. There is thus known position indicators which are actuated onbasis of hydraulic, pneumatic, electrical or other means or acombination of such means.

The object of the present invention is to provide means in order toutilize the bourdon tube principle. A bourdon tube operates as known, onthe principle that a normally noncircular or flattened closedtube-shaped member which is subjected to an internal pressure increase,will attempt to attain a circular cross-sectional shape, since thetubular space hereby will attain its largest volume. A bourdon tube isusually given the shape of a circular arch and the tube is flattened onboth sides parallelly with the axis through said circular arch. When atube is fixed at one end and the tube is subjected to an internalpressure increase, the tube will attempt to straighten out, and thedegree or amount of the straightening will take place as a function ofthe internal pressure increase. When the pressure is decreased the tubewill contract in the same fashion. The movement of the bourdon tube willin other words take place under elastic deformation in the tubematerial. There is known several types of pressure instruments where thebourdon tube principle is utilized to measure pressure variations ordifferentials.

The present invention is based upon the idea to utilize the bourdon tubeprinciple in the opposite fashion namely to sub ject the bourdon tube tomechanical influence and deformation and thereby provide internalpressure variations which via pressure transmitting means is utilized togovern an indicator mechanism, preferably including a second bourdontube. In other words, instead of transmitting pressure into movement onetransmits movement into pressure, whereafter the pressure differentialis utilized to provide a corresponding or identical movement in a secondinstrument positioned somewhere else.

In a practical embodiment of the invention the indicator systemcomprises preferably two identical bourdon tubes which areinterconnected by means of a capillar tubing, and the entire system isclosed and filled with a not compressible liquid. The member whichposition shall be remotely controlled, is arranged in mechanicalconnection with the one bourdon tube, whereby this as well as the otherbourdon tube in the position indicator will move simultaneously andproportionally with the movements of the mechanical member influencingthe one bourdon tube.

A position indicator system as above described can further in a per seknown fashion be provided with a compensating system in order tocompensate prevailing temperature and/or pressure changes, due toweather or climate conditions.

An embodiment for a position indicator in accordance with the inventionshall be described with reference to the attached schematic accompanyingDRAWING, wherein:

The reference number 2 generally designates the measuring or governingunit, 4 designates the transmitter in the shape of a capillar tubing 6,and 8 designates the indicator unit.

The governing unit 2 is influenced by a mechanical element, for instancea lever arm mounted on a butterfly valve spindle with the aim to be ableto provide remote indication of the angular position of the spindle.

The governing unit 2 comprises a support, preferably shaped as a housing10, wherein is mounted a first bourdon tube unit 12, comprising abourdon tube 14 fixedly mounted on a fitting 16, mounted to a bracket 11fixed to the housing 10. The governing member is mechanically connectedto the outer end 18 of the bourdon tube 14. As shown, the governingmember constitutes part of a valve spindle 17 provided with a lever arm19 which via a link 21 is linked to the outer end 18 ofthe bourdon tube.

From the bourdon tube member 16 to the indicator unit 8 is leading acapillar tubing 24. The indicator unit 8 comprises a bourdon tube 23,preferably identical with the bourdon tube unit in the governor 2. Thecombined support member and fitting 26 is turnable on a pivot arm 27fixed to a bracket in the indicator housing 28. To the outer end of thetubing is in known fashion arranged a pointer 30 running along a scale32.

The above-described two bourdon tube units comprises further preferablyan analogously designed compensator comprising a bourdon tube 36 in theindicator housing 8, and in the governor 2 a bourdon tube 35, and anintertransmitting capillar tubing 37 Between the outer end of thebourdon tube 36 and the turnable fitting 26 is coupled a link means 38.

The bourdon tubes with the capillar tubing constitute closed hydraulicsystems and they are preferably filled with a not compressible liquid.

The indicator system in accordance with the invention operates asfollows:

When the governing member 20 is being moved or turned by the lever arm19 on the spindle 17, for instance in the direction of the arrow A inthe FIGURE, the bourdon tube 12 will be pressed outwards, ie, thediameter will increase, resulting in that the pressure in the tube willbe reduced and this pressure reduction will via the capillar tubingimmediately be transmitted to the bourdon tube 24 in the indicator unithaving in result that the pointer 30 on the scale 32 will indicate themovement of the governing member 20. If the governing member is movingin the opposite direction such that the bourdon tube 12 will becontracted, the result will be a corresponding pressure increase in thetube which will result in that the pointer will move the other way alongthe scale 32. In other words any angular movement of the spindle 17 willbe accurately indicated on the scale 32.

The mechanical connection between the governing member 20 and thebourdon tube 12 is preferably arranged as a link mechanism, as shown.Alternatively one can, however, utilize the flexible properties of thebourdon tube and position the governing member directly biased againstthe outer part of the bourdon tube, whereby the transmittance ofmovements will take place during a sliding movement therebetween.

In order to avoid erroneous indications in consequence of pressureand/or temperature variations in the environments one should arrange aparallelly operating compensating system. A compensating systemutilizing bourdon tubes is as such known, but it is shown in the FIGUREin order to illustrate the preferred realization of the invention. Whenthe temperature in the environments for instance increases, the pressurein the bourdon tubes will increase correspondingly, but the pivotablebourdon tube unit 23 in the position indicator will be imparted a rotarymotion in opposite direction compared with the rotary motion which thebourdon tube 12 is transmitting to this tube, whereby the resultingmovement of the pointer 30 will be equal to zero, i.e., completecompensator.

Several embodiments of the invention can be conceived within the scopeof the inventive concept. The invention is thus not limited to thespecific structure herein shown and described, but may be embodied inother forms without departure from its spirit.

What is claimed is:

l. A position indicator device for remote indication of the position ofa governing member, such as the position of a valve, said indicatordevice comprising an indicator having pointer means, a first and asecond bourdon tube, said first tube being located at a measuring pointand connected to said governing member, said second tube being locatedat an indicating point and connected to said indicator, a capillartubing interconnecting said bourdon tubes in a closed fluid systemtransmitting pressure variations, means connecting said first tubemechanically to said governing member to subject said first tube tomechanical subjection generating corresponding internal pressurevariations which said capillary tubing transmits to said second tubeconnected to said indicator.

ing an additional pair of bourdon tubes, the first of which is installedat the location of said governing member, and the second of which isinstalled at the location of said indicator, said bourdon tubes beinginterconnected with a capillar tubing in a closed hydraulic system, amechanical connection being provided between a pivotable fittingsupporting the second bourdon tube and a free end of the bourdon tube atthe indicator position.

101023 n'u'i

1. A position indicator device for remote indication of the position ofa governing member, such as the position of a valve, said indicatordevice comprising an indicator having pointer means, a first and asecond bourdon tube, said first tube being located at a measuring pointand connected to said governing member, said second tube being locatedat an indicating point and connected to said indicator, a capillartubing interconnecting said bourdon tubes in a closed fluid systemtransmitting pressure variations, means connecting said first tubemechanically to said governing member to subject said first tube tomechanical subjection generating corresponding internal pressurevariations which said capillary tubing transmits to said second tubeconnected to said indicator.
 2. A position indicator device inaccordance with claim 1 wherein a housing is provided for saidindicator, a pivotable armature supported in said housing has saidpointer means fixed thereto, and said capillar tubing is connected tosaid pivotable armature.
 3. A position indicator device in accordancewith claim 1 wherein said governing member is mechanically connected toone end of said first tube and the other end is fixed.
 4. A positionindicator device in accordance with claim 1, wherein said deviceincludes a compensating system comprising an additional pair of bourdontubes, the first of which is installed at the location of said governingmember, and the second of which is installed at the location of saidindicator, said bourdon tubes being interconnected with a capillartubing in a closed hydraulic system, a mechanical connection beingprovided between a pivotable fitting supporting the second bourdon tubeand a free end of the bourdon tube at the indicator position.